Eric D. Collins

Effect of a selective dopamine D1 agonist (ABT-431) on smoked cocaine self-administration in humans.

Rationale: Data in laboratory animals suggest that D1 receptor agonists may have potential utility for the treatment of cocaine abuse. Objective: The effects of ABT-431, a selective agonist at the dopamine D1 receptor, on the reinforcing, cardiovascular and subjective effects of cocaine were investigated in humans. Method: Nine experienced cocaine smokers (8M, 1F), participated in nine self-administration sessions while residing on an inpatient research unit: three doses of ABT-431 (0, 2, 4 mg IV) were each given in combination with three doses of smoked cocaine (0, 12, 50 mg). ABT-431 was intravenously administered over a 1-h period immediately prior to cocaine self-administration sessions. A six-trial choice procedure (cocaine versus

Comparison of intravenous and intranasal heroin self-administration by morphine-maintained humans

5 merchandise vouchers) was utilized, with sessions consisting of: (a) one sample trial, where participants received the cocaine dose available that day, and (b) five choice trials, where participants chose between the available cocaine dose and one merchandise voucher. Results: ABT-431 did not affect the number of times participants chose to smoke each dose of cocaine, but produced significant dose-dependent decreases in the subjective effects of cocaine, including ratings of “High,”“Stimulated,” dose liking, estimates of dose value, “Quality,” and “Potency.” Furthermore, there was a trend for ABT-431 (4 mg) to decrease cocaine craving. ABT-431 also increased heart rate, while decreasing systolic and diastolic pressure at each dose of cocaine. Conclusions: These data suggest that D1 agonists may have potential utility for the treatment of cocaine abuse.

Sensitive and selective liquid chromatographic assay of memantine in plasma with fluorescence detection after pre-column derivatization.

Abstract Eight heroin-dependent individuals, maintained on divided daily doses of oral morphine, participated in a 2.5-week inpatient study comparing the effects of intranasal (IN) (placebo, 12.5, 25, 50, 100 mg) and intravenous (IV) (placebo, 6.25, 12.5, 25, 50 mg) heroin. Each morning, participants received

Behavioral naltrexone therapy: An integrated treatment for opiate dependence

20 and a sample dose of heroin, and each afternoon they had the opportunity to self-administer all or part of the morning heroin dose or money amount. Participants responded under a modified progressive-ratio schedule (PR 50, 100, 200, 400, 800, 1200, 1600, 2000, 2400, 2800) during a ten-trial self-administration task. During each trial, participants could respond for 1/10th of the heroin dose or 1/10th of the money amount. The total amount of heroin and/or money chosen during the self-administration task was given at the end of the task. Thus, participants received drug and/or money twice each day: once during the morning sample session and once during the afternoon self-administration session. Participants received IV solution and IN powder simultaneously during each dosing; only one route contained active drug. Heroin produced dose-related increases in break point values by both routes of administration. Although IV heroin was approximately four-fold more potent than IN heroin, the maximal break point values for both routes were not significantly different. A similar difference in potency between the IV and IN routes was found for several ratings of subjective effects (e.g., “I feel a good drug effect,”“I feel high”), but maximal subjective ratings were lower for IN compared to IV heroin. These results suggest that the reinforcing efficacy of heroin is similar by the two routes of administration, but that IN heroin is less potent than IV heroin. The results also underscore the importance of evaluating drug self-administration in the evaluation of the abuse liability of drugs.

Memantine increases cardiovascular but not behavioral effects of cocaine in methadone-maintained humans

A procedure was developed for the determination of memantine in plasma using liquid chromatography with fluorescence detection. Following a liquid-liquid extraction from 1 ml of plasma containing the internal standard amantadine, the extract was derivatized at room temperature with dansyl chloride, and the highly fluorescent derivatives were chromatographed with a reversed-phase C18 column and a mobile phase of phosphate buffer and acetonitrile. Dansylated memantine and amantadine were eluted in less than 13 min with no interference from endogenous material. The calibration curve was linear over the concentration range of 3-400 ng/ml with inter- and intra-assay imprecision (C.V.) of less than 10%. The limit of quantitation was 3 ng/ml, and no major antidepressant, neuroleptic or their respective metabolites interfered with the quantitation of memantine. This method could also be applied to the quantitation of amantadine.

Amantadine does not modulate reinforcing, subjective, or cardiovascular effects of cocaine in humans

Treatment of opiate dependence with naltrexone has been limited by poor compliance. Behavioral Naltrexone Therapy (BNT) was developed to promote adherence to naltrexone and lifestyle changes supportive of abstinence, by incorporating components from empirically validated treatments, including Network Therapy with a significant other to monitor medication compliance, the Community Reinforcement Approach, and voucher incentives. An overview is presented of the BNT treatment manual. In an uncontrolled Stage I trial (N = 47), 19% completed the 6-month course of treatment. Retention was especially poor in the subsample of patients who were using methadone at baseline (N = 18; 39% completed 1 month, none completed 6 months), and more encouraging among heroin-dependent patients (N = 29; 65% completed 1 month, 31% completed 6 months). Thus, attrition continues to be a serious problem for naltrexone maintenance, although further efforts to develop interventions such as BNT are warranted.

Depot naltrexone: long-lasting antagonism of the effects of heroin in humans

Previous work has suggested that maintenance on the noncompetitive N-methyl-d-aspartate (NMDA) antagonist, memantine, increased the subjective effects of smoked cocaine in experienced cocaine users. To determine whether this phenomenon occurs in opioid-dependent individuals, eight (seven male, one female) methadone-maintained cocaine smokers participated in a 47-day inpatient and outpatient study to assess the effects of memantine on smoked cocaine self-administration, subjective effects, and cardiovascular responses. The participants were maintained on memantine (0 mg and 20 mg daily) for 7-10 days prior to laboratory testing, using a double-blind crossover design. Under each medication condition during inpatient phases, participants smoked a sample dose of cocaine base (0, 12, 25, and 50 mg) once, and were subsequently given five choice opportunities, 14 min apart, to self-administer that dose of cocaine or receive a merchandise voucher (US 5.00 dollars). Each cocaine dose was tested twice under each medication condition, and the order of medication condition and cocaine dose were varied systematically. Memantine maintenance did not alter the subjective or reinforcing effects of cocaine. Several cardiovascular responses, however, including peak and initial diastolic pressures following cocaine, were significantly greater during memantine maintenance, although these elevations were not clinically significant. Taken together, these findings corroborate earlier data suggesting that this dose of memantine will not be helpful in the pharmacotherapy of cocaine abuse.

Anesthesia-assisted vs buprenorphine- or clonidine-assisted heroin detoxification and naltrexone induction: a randomized trial.

Data from several clinical studies have suggested that amantadine, which has dopaminergic agonist and glutamatergic antagonist effects, may be useful for the treatment of cocaine dependence. The interaction between amantadine and smoked cocaine was examined in 10 cocaine smokers (7 men, 3 women), who participated in a 26-day inpatient study. Participants were maintained on amantadine (0 and 100 mg bid) for 5 days prior to laboratory testing, using a double-blind crossover design. Under each medication condition, participants smoked a sample dose of cocaine base (0, 12, 25, and 50 mg) once, and were subsequently given five choice opportunities, 14 min apart, to self-administer that dose of cocaine or receive a merchandise voucher (

Self-administration of intravenous buprenorphine and the buprenorphine/naloxone combination by recently detoxified heroin abusers

5.00). Each cocaine dose was tested twice under each medication condition, and the order of medication condition and cocaine dose varied systematically. Cocaine produced stimulant-like reinforcing, subjective, and physiological effects. Amantadine maintenance did not modify the choice to self-administer smoked cocaine. These findings, taken together with the decidedly mixed literature, suggest that amantadine (100 mg bid) will not have a role in the treatment of cocaine dependence.